Chairs having articulated, flexible backrest parts for achieving desired support and comfort for the user are known in the art. Such chairs are used, for example, in banquet and conference facilities where back comfort for the seated individual is desirable. Chairs of this type typically are stackable and have molded backrest parts and peripheral frame parts of hollow construction to enable interconnection of upper and lower backrest parts which are flexible one relative to the other. Various types of flexible spring arrangements for joining the upper and lower backrest parts of such chairs are known. An example of such a spring arrangement is disclosed in U.S. Pat. No. 4,603,904 which is assigned to the same assignee as the assignee herein.
The chair disclosed in U.S. Pat. No. 4,603,904 includes an articulated, flexible backrest having a spring means that includes an elongated plastic support strut having a hollow passageway that is fitted with a flexible core. The flexible core comprises a wire cable or the like whose structural specification is selected to limit to some degree the flexing angle of the backrest's upper part. The spring means serve positively to join the upper and lower backrest portions to prevent translational movement therebetween. As the spring means are flexed, the wire cable secured in the passageway of the plastic support strut limits the elongation and ultimate yield or breaking point of the strut. The cable controls elongation of the strut to permit flexing and yet prevents tensile failure by insuring that the plastic support strut is not flexed beyond the tensile limit of the material from which it is constructed. A problem encountered with this structure derived from change in characteristics of the wire cable and spring strut after extended periods of time or unusual use or abuse.
The herein invention focuses on avoiding such problems by providing a flexible spring assembly which includes specially constructed holder means for the spring having restrictive engagement means which will not change in function characteristics and yet prevent flexing of the spring beyond the tensile limit of the material from which it is constructed.